Ed Miliband has broken the 'natural, male, top-down order of things' by beating his elder brother. Photograph: Stefan Rousseau/PA

I am genuinely perplexed by the fury some express about the so-called "fratricidal" nature of Ed Miliband's victory over his elder brother David. Jon Cruddas's line that "it wouldn't happen in my family" (half-mafia, half-EastEnders), the belief that brother shouldn't stand against brother appears to be a paean to loving your relations. But it seems to me something else: a sort of feudal belief in the primacy of the eldest son, of the natural, male, top-down order of things.

Would anyone be making these criticisms if David had won? Of course not: the elder slaying the ambitions of the younger is perfectly permissible. So what appears to be a defence of family loyalty is in fact a defence of primogeniture: it's anti-meritocratic and it's about knowing your place. Heaven forfend if Ed had been female: in this sort of ordering, all girls, however talented or aged, come lower than the youngest of boys. See the royal family for details.

So Ed followed David into Labour politics – that's hardly surprising, considering their upbringing. Perhaps they would have had happier lives if they'd been drawn to different things. But should the younger brother really be obliged to go into some unwanted, less threatening profession instead? Is he not entitled to the same array of choices and dreams?

I'm an older sibling, by the way. If my younger brother chose to go into journalism and was more successful than me – well, I don't see why my ambitions should take precedence over his. Elder children are bossy, demanding, serious types and it's about time our sense of entitlement was challenged. As long as I got a bit of the fun-loving, carefree recklessness of the second-born in exchange.